Patent GB-379330-A (GB)
Title: Improvements relating to the control of railway traffic
IPC: B61L23/12
Filed: 1931-05-21
Abstract: 379,330. Railway signalling systems. PETER, L. H. and WESTINGHOUSE BRAKE & SAXBY SIGNAL CO., Ltd., 82, York Road, King's Cross, London. May 21, 1931, No. 15020. [Class 105.] A block section railway signalling system has all the signals, points, or other trafficgoverning devices, such as token instruments, along a suitable length of track controlled from a central office and the setting of the devices is further subjected to control by the traffic conditions in the block section or in an adjacent block section by means not involving continuous track circuits extending throughout the block section. Each block section is shown in Fig. 1 provided with a short entrance section 3 with a track relay TA and with a short detector relay section 4 in which the detector relay DA is only energized while the train is in the detector section ; the remainder of the block section may use metal sleepers since insulation of the rails thereof is not necessary. The signal A is normally cleared by a code signal from the central office which closes the contact C in the circuit to the signal relay R. This circuit includes a front contact L1 of a locking relay L which is de-energized on the entrance of a train into the block and is only re-energized when the train has passed through the short entrance section 11 and detector section 12 of the block ahead. The locking relay L for signal A is held by a stick circuit from battery G over wire 7, front contact T1 of its own entrance section track relay TA, and front contact L3, L4 of locking relay L. The pick-up circuit of relay L includes its own back contact L2, L3, front contact T2 of the block ahead entrance relay TB, front contact F1 of a block control relay F, and back contact D2 of the block ahead detector relay DB. The block control relay F is picked up by its winding 6 when a train in the ahead entrance section 11, having caused contact T3 of track relay TB to drop, enters detector section 12 to close contact D3 of detector relay DB ; the relay F is stuck over its own front contact F2 and front contact T3 when the train leaves the entrance track relay section 11 and until it leaves the detector section 12. It is evident therefore that the locking relay L is only picked up if the train has entered and passed through both the ahead entrance track relay and detector sections 11, 12 to cause the picking up of relay F to close contact F1 and the subsequent closure of front contact T2 and back contact D2, and that only under these conditions can the signal A be again cleared to permit the passage of another train. The detector relays may be replaced by treadles or by relays inductively or optically affected by the passage of the train, Figs. 2, 5 and 6 (not shown). To prevent the restoration unless the complete train has passed there is provided a relay Q, Fig. 3, which is energized from a transformer device 19, 20 over its own front contact Q1 but is de-energized when an end-carriage inductive device diverts the flux from the secondary winding 20 whereupon a back contact Q2 is then closed to complete the pickup circuit of the locking relay. The relay Q is only picked up again when a contact RB1 of the ahead signal relay RB closes. In another arrangement the locking relay L is only energized when two inductively actuated axle counting devices are in phase. In the arrangement diagrammatically represented in Fig. 8 the train when passing through the entrance sections of the block ahead controls relays LB and F whereby a code is transmitted over line wires 25 between code devices CB, CA to pick up the locking relay L. The signal is cleared by a code over line wires 26 from the central office actuating code device CG and when the train enters a return indicating code is started by the dropping of contact L5. During fog conditions a " fog overlap " is provided by arranging for the locking relay L not to be re-energized until the train reaches a point further ahead, such as the entrance to the block section second ahead. Fig. 9 shows such an arrangement wherein under fog conditions a fog detector FD employing a lightsensitive device de-energizes a relay FR to reverse the connection of battery G, so that the block control relay F which is a polarized one has its contacts FP1, FP2 at reverse instead of at normal as is shown. Accordingly when the train passes into section B the relay L will not be picked up since the dropped relay BL has opened its contact BL2 ; however the back contact BL1 closes a stick circuit for the winding 6 of the block control relay F over reverse contact FP1, front contacts F3, T4 and back contact D4. As no fog relay is provided for block B the relay BL will be re-energized when the train has entered the block ahead of B and thereupon the front contact BL2 completes the pick-up circuit for relay L of section A over front contacts F1, T2 and back contact D2. The contacts D2, D3, D4, T2, T3, T4 are those of the detector and short entrance section relays of block B ; contacts F1, F2, F3 are contacts of the block control relay F. In a token traffic control system the instruments may be locked from the central control office to prevent withdrawal of tokens.